“Tunable parameters” (sometimes also referred to as “tunable variables” or simply “tunables”) are variables that affect the operation of an operating system kernel by setting table sizes and system thresholds, among other things. Tunable parameters also control characteristics of processes, files, and system activity, and thus provide a way in which operating system kernels can be optimized for particular computers or installation or usage circumstances. For example, a “maxusers” tunable parameter may be provided to adjust the size of tables, arrays, buffers, etc. to optimize system performance for the expected number of users on a system. System administrators will be familiar with the tunable parameters that optimize their operating system kernels to various computer systems, installation, and/or usage circumstances. In some instances, kernels are recompiled and relinked for tuning, and to add drivers and subsystems.
Many tunable parameters are related to each other by constraints. For example, the number of files each user is allowed to have opened must necessarily be less than the number of files allowed opened on the whole system. Administrators who wish to change related values must be careful to change the tunables in the proper order to avoid violating such constraints. This need for extra care makes tuning the system more difficult.